This invention relates to improvements in water treatment plants and, more particularly, to improvements in such plants utilizing tubular settling devices that settle the water at low Reynolds number flows. The invention is applicable to both water and wastewater treatment.
Packaged water and wastewater treatment plants have found ready acceptance by small communities, motels, recreational areas and the like. The plants can be operated with a minimum of operator control. When used for providing potable drinking water, they are able to provide high clarity water on a fail-safe basis.
A packaged water treatment plant of the above type is disclosed in Hansen et al, U.S. Pat. No. 3,482,695. The plant therein disclosed utilizes a settling means comprising a plurality of small diameter tubes which permit settling of settleable material in a short period of time before passing the water through a filter. The water passes through the tubes at a low Reynolds number flow, the velocity being sufficiently low to provide streamlined laminar flow through the tubes.
The plant comprises means to achieve rapid coagulant chemical dispersion and automatic pH control, mechanical flocculation, a settling basin comprising the settling tubes as above described, filter means and the necessary plant and process controls. A tank is provided for receiving the filtered water and means are provided automatically to pump water from the tank back through the filter and the settling means when backwashing becomes necessary, thereby simultaneously to backwash the two.
A problem arises with plants of the above type, however, when it is desired to increase their capacity. Often the allowable width of the plant is restricted, although it is possible to increase the length. Furthermore, problems sometimes arise in achieving a uniform distribution of the water through all of the settling tubes. The tubes function more efficiently if the flow through each of the tubes is substantially the same.
Accordingly, it is an object of the present invention to provide a water treatment plant of the foregoing type that will permit more cost-effective design configurations and provide treated water in larger capacities than has heretofore been possible.
It is a further object of the present invention to provide such a plant that can be used in both package treatment plants of the foregoing type and also in large plants, and which will be applicable to both water and waste water treatment.
It is a further object of the present invention to provide such a plant when there are restrictions on its allowable width.
It is a still further object of the present invention to provide such a plant with improved flow distribution through the tubes in the settling basin such that the flow through each will be substantially more uniform than has heretofore been possible, thereby to increase settling efficiency.